#include<iostream>

#include<cstdio>

#include<algorithm>

#define INF 99999999

#define MAXN 1010

#define unionn(x,y) fa[y]=x

#define eps 0.000001

using namespace std;

int fa[MAXN],n,m,s,t,maxn,minx,ll=INF,rr=INF;

double ans=;

struct asd{

    int x,y,v;

} r[];

inline int find(int x)

{

    if(fa[x]!=x) fa[x]=find(fa[x]);

    return fa[x];

}

inline bool cmp(asd x,asd y)

{

    return x.v<y.v;

}

inline int gcd(int a,int b)

{

    return b== ? a : gcd(b,a%b);

}

int main()

{

    scanf("%d%d",&n,&m);

    for(int i=;i<=m;i++)

        scanf("%d%d%d",&r[i].x,&r[i].y,&r[i].v);

    scanf("%d%d",&s,&t);

    sort(r+,r++m,cmp);

    for(int i=;i<=m;i++)

    {

        for(int j=;j<=n;j++) fa[j]=j;

        unionn(find(r[i].x),find(r[i].y));

        minx=maxn=r[i].v;

        if(find(s)==find(t))

        {

            double anss=ans;

            ans=(double)maxn/minx;

            if(ans-eps<anss-eps)

                ll=maxn,rr=minx;

            break;

        }

        for(int j=i+;j<=m;j++)

            if(find(r[j].x)!=find(r[j].y))

            {

                unionn(find(r[j].x),find(r[j].y));

                minx=min(minx,r[j].v);

                maxn=max(maxn,r[j].v);

                if(find(s)==find(t))

                {

                    double anss=ans;

                    ans=(double)maxn/minx;

                    if(ans-eps<anss-eps)

                        ll=maxn,rr=minx;

                    else ans=anss;

                    break;

                }

            }

    }

    if(ll==INF) { printf("IMPOSSIBLE\n"); return ;}

    if((double)ll/rr==ll/rr) printf("%d",ll/rr);

    else

    {

        while(gcd(rr,ll)!=)

        {

            int mid=gcd(rr,ll);

            ll/=mid; rr/=mid;

        }

        printf("%d/%d\n",ll,rr);

    }

}